Image transfer process

ABSTRACT

A device for transferring dielectric imaging material from an image bearing substrate to an image receiving substrate at high speed through the use of electrical bias and pressure. Pressure is provided by a conductive blade.

United States Patent Gerace et al.

1 IMAGE TRANSFER PROCESS {75] Inventors: Robert E. Gerace, Fairport; William L. Gary, Lyuns; Charles J. Hull, Jr., Fairport, all of NY.

[73] Assignee: Xerox Corporation, Stamford.

Conn.

[22] Filed: Dec. 28, 1973 [21] App]v No.: 429.247

[52] U.S. Cl 118/637; 117/17.5

[51] Int. Cl G03g 13/16 [58] Field of Search rrrrr H 118/637; 117/175; 96/1.4;

[56] References Cited UNITED STATES PATENTS 3,029,779 4/1962 Hornbostel 118/104 1 June 10, 1975 3,155.546 11/1964 Dirks r. IlS/DIG. 23 3,247.794 4/1966 Zabiak 117/1715 3.477.846 11/1969 Weigl et a1 117/175 Primary ExaminerLouis K. Rimrodt Assistant E.mminer-Douglas Salser [57] ABSTRACT A device for transferring dielectric imaging material from an image bearing substrate to an image receiving substrate at high speed through the use of electrical bias and pressure. Pressure is provided by a conductive blade.

10 Claims, 2 Drawing Figures PATENTEDJUH I 0 ms FIG. I

" FIG. 2

1 IMAGE TRANSFER PROCESS BACKGROUND OF THE INVENTION The present invention relates in general to the transfer of images from an image bearing surface to an image receiving surface and more particularly to a device to accomplish such transfer by means of electrical charge and pressure.

There are numerous modern methods for converting optical images into graphic images and to produce numerous copies of such images. In most instances elec trical charges of many types are employed and the image material is generally a dielectric material which retains an electrostatic charge at least during the production of the image and in some cases the transfer of such images to a final copy substrate. The most common commercial method is known as xerography which employs toner particles such as carbon black or colored resins for the production of images. More recently other imaging methods have been discovered such as the photoelectrophoresis method typically described in US. Pat. No. 3,384,565 to Tulagin et al. which patent is hereby incorporated by reference. Another recently discovered imaging method which pro vides images composed of dielectric material is typically described in US. Pat. No. 3,707,368 to Van Dorn which patent is also hereby incorporated by reference.

Common to these imaging methods is the need for a convenient, fast and high quality image transfer method so that the image can be placed upon a final copy substrate which is different than the substrate upon which it is orginally produced. The results of efforts in the manifold imaging art to perform such transfer is typically represented by such patents as U.S. Pat. No. 3,658,519 and U.S. Pat. No. 3,706,553 to Menz. In accordance with such methods the dielectric image is transferred by employing residual electrostatic charges retained in the image and static electrical charges residmg on an insulating substrate. By means of coulombic attraction and the rearrangement of electrical charges an image is transferred from an image bearing substrate to an image receiving medium. Also, and particularly due to the manifold imaging process as described in the aforementioned US. Pat. No. 3,707,368, a pressure transfer system has been devised typically described in US. Pat. No. 3,708,288 to Lin. As is indicated by these above mentioned patents the transfer methods are enhanced by wetting the image receiving medium with a liquid material commonly termed an activator.

With the development of high speed and very high speed printing methods the use of such prior art meth' ods have proven difficult particularly for high quality, high speed image production. Accordingly, there is desired a device which simplifies the image transfer method and eliminates the need for liquid activators to provide high fidelity transfer methods.

SUMMARY OF THE INVENTION It is, accordingly, an object of this invention to provide a transfer apparatus for transferring dielectric image material from an image bearing substrate to a copy medium.

Another object of this invention is to provide an image transfer device which is capable of operating at very high speeds.

Another object of this invention is to provide a device for transferring dielectric images at very high speed and high fidelity without the need for applying a liquid activator to the copy medium.

These and other objects will become apparent upon reading the following description of the invention.

In accordance with this invention there is provided an image transfer device which comprises a round tipped electrically conductive blade in juxtaposition to a back-up roller adapted to receive an image-bearing medium and an image receiving medium therebetween under pressure. In addition the device provides means for exerting an electrical bias between the electrically conductive blade and the roller. The bias assists in the transfer of dielectric imaging material which in most cases possesses a static electrical charge. Rotation of the backup roller while feeding through the image bearing and receiving media provides an extremely rapid means for high fidelity transfer of dielectric image material. The pressure applied to the media combined with an electrical bias provides the improved transfer without the need for applying an activator to the image receiving medium. The image bearing and receiving media are pulled through the nip of the blade and roller by an independent drive means for the media.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of the apparatus of this invention will become apparent upon consideration of the detailed disclosure especially when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side sectional view diagrammatically illustrating one of the imaging methods which provides a dielectric image useful in the process of this invention.

FIG. 2 is a side sectional view of the apparatus of this invention,

Referring now to FIG. I there is shown a typical manifold imaging process wherein an imaging layer, structurally fracturable in response to the combined effects of an applied electrical field and exposure to electromagnetic radiation to which it is sensitive, is sandwiched between a donor and a receiver layer. A more complete description of such a process is found in the aforementioned US. Pat. No. 3,707,368 In FIG. 1 there is shown imaging layer 12 being fractured after exposure to image 29 as receiver layer 16 is being separated from donor layer 17 under the influence of an electrical field applied through potential source 28 and resistor 30. The particular instance described herein employs a conductive receiver 16 as an electrode while the transparent electrode 18 is employed to complete the electrical circuit. Imaging layer 12 fractures in response to the light image 29 providing complementary negative and positive images on the receiver and donor sheets,

One of the images such as that residing on receiver I6 is then employed in the apparatus of this invention. Referring now to FIG. 2 there is shown image bearing substrate 1 which in this example, is the receiver sheet of FIG. 1. In a preferred embodiment image bearing medium 1 is a closed loop with the imaging process of FIG. I taking place at the opposite side of the loop from the point of transfer indicated in FIG. 2. Thus image bearing medium 1 can be a reusable receiver element in the imaging process exemplified by the manifold imaging process of FIG. 1. Image receiving medium 3 is fed simultaneously with image hearing medium I between electrically biased blade 5 on mount 7 and conductive roller 9. Roller 9 is illustrated in FIG. 2 as having a conductive metal core 11 and a resilient outer portion 13. Although roller 9 can be a rigid roller such as a metal roller throughout, in the preferred embodiment, at least the outer surface of roller 9 is resilient because such resiliance allows for small variations in the diameter of the roller, thickness of the materials passing between blade 5 and roller 9 and provides some protection against damage due to pressure exerted by blade 5 against the image bearing and receiving media. For example roller 9 can be constructed of a metallic inner core with a rubber or thermoplastic coating 13. Typical materials include conductive rubber and plastic materials. To assist in the transfer a bias is placed across blade 5 and roller 9 by means ofa voltage source 15. While the bias depends upon many factors such as the dielectric constants and thickness of the image material, image bearing and receiving media, it is typically in the range of from about 600 to about 900 volts when images produced as in the manifold imaging process depicted in FIG. 1 are transferred from an electrically insulating image bearing medium to an electrically insulating receiving medium.

In order to protect the image bearing and image receiving media yet provide sufficient pressure at the tip of the blade 5 pressing against image bearing medium 1 blade 5 is rounded to a radius of up to about 0.1 inch. Most usually the tip of blade 5 is rounded to a radius of from about 0.050 to about 0.075 inches while excellent results are obtained with a radius of from about 0.060 to about 0.065 inches. A sharp knife edge tends to cut the image bearing or image receiving media upon stopping or starting of the device. However, it has been found that by rounding the edge slightly excellent image transfer is provided without damage to the media. Another means for preventing damage to the media passing between the blade and roller is to mount blade 5 in a cushioned mount such as providing a resiliant mount 7 or a spring loaded mount, not shown, such that variations in the diameter of roller 9 may be compensated by movement of the blade in a plane normal to the image bearing and receiving media.

Improved results are obtained with the device of this invention wherein blade 5 is mounted at an angle to the horizontal plane of the roller axis. As shown in FIG. 2 blade 5 is mounted at a l0 angle to the horizontal plane which angle is not critical but has been found to be preferred. Through the use of a tangentially pivoted spring loaded mount with self alligning blade to compensate for such problems as roll run-out and cylindrical, the tracking of the two media is improved. Thus under very high speed conditions the media passing between the blade and the roller are kept together on the roller to effect high fidelity transfer.

Through the use of blade 5 a great amount of pressure is brought to bear upon the media passing between the blade and the roller with a small amount of force. Thus, for example, a total force of about 2 lbs. exerted on a 38 inch wide blade having a radius of about 0.062 inches produces over 300 lbs per sq. inch by proper adjustment of the spring load between the blade and the roller.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

1. An image transfer device which comprises an electrically conductive round tip blade in juxtaposition to an electrically conductive backup roller adapted to ac cept under pressure an image bearing medium and an image receiving medium therebetween. means to apply an electrical bias between said blade and said roller, said tip having a radius of from about 0.05 inches to about 0.l inches, said blade being mounted at an angle to the horizontal plane of the axis of said roller and said roller and media being driven in the same direction.

2. The device of claim 1 wherein said roller is rigid.

3. The device of claim 1 wherein said roller is resilient.

4. The device ofclaim 2 wherein said blade is cushion mounted.

5. The device of claim 1 wherein said blade is cushioned mounted.

6. The device of claim 1 wherein said image bearing substrate is a closed loop.

7. The device of claim 1 wherein said roller is rigid and said blade is cushion mounted.

8. The device of claim 1 wherein said blade tip has a radius in the range of from about 0.06 inches to about 0.065 inches.

9. The device of claim 1 wherein said blade tip radius is in the range of from about 0.050 to about 0.075 inches.

10. The device of claim 1 wherein said blade tip radius is in the range of from about 0.060 to about 0.065

inches. 

1. An image transfer device which comprises an electrically conductive round tip blade in juxtaposition to an electrically conductive backup roller adapted to accept under pressure an image bearing medium and an image receiving medium therebetween, means to apply an electrical bias between said blade and said roller, said tip having a radius of from about 0.05 inches to about 0.1 inches, said blade being mounted at an angle to the horizontal plane of the axis of said roller and said roller and media being driven in the same direction.
 2. The device of claim 1 wherein said roller is rigid.
 3. The device of claim 1 wherein said roller is resilient.
 4. The device of claim 2 wherein said blade is cushion mounted.
 5. The device of claim 1 wherein said blade is cushioned mounted.
 6. The device of claim 1 wherein said image bearing substrate is a closed loop.
 7. The device of claim 1 wherein said roller is rigid and said blade is cushion mounted.
 8. The device of claim 1 wherein said blade tip has a radius in the range of from about 0.06 inches to about 0.065 inches.
 9. The device of claim 1 wherein said blade tip radius is in the range of from about 0.050 to about 0.075 inches.
 10. The device of claim 1 wherein said blade tip radius is in the range of from about 0.060 to about 0.065 inches. 